Plus Me
I never signed up for Facebook and I don't anticipate using Google+ as a not-Facebook, but I'm plenty curious about the UI and design and so have signed up to help train Google's social advertising algorithms. Google+ seems to have a lot of rules – use your real name and gender, no companies allowed, etc – but the experience of rules being lifted over time (assuming they will be) is better than the one of rules being added over time (I'm looking at you, Twitter).